How to create a text file and insert data to that file on Android using Kotlin?

This example demonstrates how to create a text file and insert data to that file on Android using Kotlin.

Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.

Step 2 − Add the following code to res/layout/activity_main.xml.

<?xml version="1.0" encoding="utf-8"?>?
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:tools="http://schemas.android.com/tools"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   tools:context=".MainActivity">
   <TextView
      android:id="@+id/textView"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_centerHorizontal="true"
      android:layout_marginTop="70dp"
      android:background="#008080"
      android:padding="5dp"
      android:text="TutorialsPoint"
      android:textColor="#fff"
      android:textStyle="bold" />?
   <EditText
      android:id="@+id/editText"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:layout_below="@+id/textView"
      android:layout_marginTop="40dp"
      android:ems="10">
      <requestFocus />
   </EditText>
   <Button
      android:id="@+id/button1"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_below="@+id/editText"
      android:layout_centerInParent="true"
      android:layout_margin="5dp"
      android:background="@android:color/holo_orange_light"
      android:onClick="saveTextFile"
      android:text="Save File"
      android:textColor="@android:color/background_dark"
      android:textStyle="bold" />
</RelativeLayout>

Step 3 − Add the following code to src/MainActivity.kt

import android.content.Context
import android.os.Bundle
import android.view.View
import android.widget.EditText
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import java.io.FileOutputStream
import java.io.OutputStreamWriter
class MainActivity : AppCompatActivity() {
   lateinit var editText: EditText
   override fun onCreate(savedInstanceState: Bundle?) {
      super.onCreate(savedInstanceState)
      setContentView(R.layout.activity_main)
      title = "KotlinApp"
      editText = findViewById(R.id.editText)
   }
   fun saveTextFile(view: View) {
      try {
         val fileOutputStream: FileOutputStream = openFileOutput("mytextfile.txt", Context.MODE_PRIVATE)
         val outputWriter = OutputStreamWriter(fileOutputStream)
         outputWriter.write(editText.text.toString())
         outputWriter.close()
         //display file saved message
         Toast.makeText(baseContext, "File saved successfully!", Toast.LENGTH_SHORT).show()
      }
      catch (e: Exception) {
         e.printStackTrace()
      }
   }
}

Step 4 − Add the following code to androidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
   package="com.example.q11">
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
   <application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:roundIcon="@mipmap/ic_launcher_round"
      android:supportsRtl="true"
      android:theme="@style/AppTheme">
      <activity android:name=".MainActivity">
         <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
      </activity>
   </application>
</manifest>

Let's try to run your application. I assume you have connected your actual Android Mobile device with your computer. To run the app from android studio, open one of your project's activity files and click the Run  icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen